According to the OED, in an un-updated entry, "coronate" is a rare synonym for "crown." However, I can see the possibility of using it to prevent ambiguity when the word "crown" could have more than one meaning, such as in "Don't Crown Hillary," which (at least in American English) could mean, "Don't hit her on the head (the crown)." There's another meaning for the verb "crowned" as well, as a certain stage in the birthing process, the details of which I won't go into here. So the headline I saw read "Don't Coronate Hillary," and I think that's a perfectly good use of this verb. As a side note, both "coronated" and "crowned" can be used in the following ways: as a past tense intransitive verb, as the past participle of a verb, and as a participial adjective. And rather than be a back-formation from "coronate," this is a real, true, oooold, Latin-based word that appears in every dictionary bigger than a thimble. ;-)